South Korea’s spy agency says North Korea appears to have sent additional troops to Russia, after its soldiers deployed on the Russian-Ukraine fronts suffered heavy casualties.

Ukrainian troops holding positions in Kursk say the North Koreans have reappeared on the battlefield and become even more formidable foes.

On Monday, the U.S. joined North Korea, Iran and 15 other countries in voting against a U.N. General Assembly resolution drafted by Ukraine that blamed Russia for the “devastating and long-lasting” war; the resolution passed with 93 votes in favor.